Gun registration schemes have been disabled for criminals because requiring them to register a gun they are forbidden to own would violate their 5th Amendment rights. I would assume that if ballistic fingerprinting ever became law, a form would be offered at time of sale where you would be required to waive any claim of 5th Amendment right injury from any governmental authority's use of the ballistic data. Don't sign the form - you don't get the gun.
Label: Sarcastic